Subwoofer acting strange, any thoughts?

George Othen

George Othen

Enthusiast
Hello everyone,

I've got a pair of Yamaha sw205's and one of them has developed an unusual issue.

With the gain turned on full the sub barely cranks out any bass.

I can't think of a correct way of stating the issue but let's say they have a 10 level volume, with the working sub on volume level 3 the other sub requires level 10 to reach the same output.

When I turn up the volume on my receiver, the broken sub seems to suddenly decide that it is in fact set to volume level 10 and distortion and what sounds like bottoming out begins happening. Then it switches back to acting like it's set to volume level 3.

From what I can gather it seems to be based on the amplitude of the input but I can't think why this would happen.

I've tested it with high level and low level input and it's the same result

Does anyone have any idea what could be causing this?

thanks :)
 
TLS Guy

TLS Guy

Seriously, I have no life.
Hello everyone,

I've got a pair of Yamaha sw205's and one of them has developed an unusual issue.

With the gain turned on full the sub barely cranks out any bass.

I can't think of a correct way of stating the issue but let's say they have a 10 level volume, with the working sub on volume level 3 the other sub requires level 10 to reach the same output.

When I turn up the volume on my receiver, the broken sub seems to suddenly decide that it is in fact set to volume level 10 and distortion and what sounds like bottoming out begins happening. Then it switches back to acting like it's set to volume level 3.

From what I can gather it seems to be based on the amplitude of the input but I can't think why this would happen.

I've tested it with high level and low level input and it's the same result

Does anyone have any idea what could be causing this?

thanks :)
Without obtaining the circuit is is not possible to say, if the problem is the sub.

I would try another sub cable, in case the problem is a bad connection in a sub cable.
 
Last edited:
lovinthehd

lovinthehd

Audioholic Jedi
Tried swapping sub cables maybe see if the problem follows the switch or not? Kinda sounds like a sub amp going bad, tho.
 
Bucknekked

Bucknekked

Audioholic Samurai
I have a sub which suffers from a similar sounding problem. After doing what the previous posters suggested, it came down to the bash amp in the unit. The amp in mine was the defective piece. And as the economics of audio work out, that means a tough choice. To fix mine meant pretty much replacing the amp and the cost of that isn't worth it given what the sub is worth.

Right now, I use the sub as a doorstop. Its the best use I could find outside of a landfill.

YMMV, hope its the cable
 
George Othen

George Othen

Enthusiast
I checked with the other sub's cable and it's the same problem. :(
 
TLS Guy

TLS Guy

Seriously, I have no life.
I checked with the other sub's cable and it's the same problem. :(
Well that sub is done. It is a $219 sub from 2002/2003. So it has served you well. Since it is a servo sub, you can not just replace the plate amp with one form Parts-Express or other vendor. I'm afraid it is the end of the line for that sub.
 
George Othen

George Othen

Enthusiast
I'm still a bit miffed and slightly stubborn xD. I will try and fix it, can't replace it atm so I guess I'll just hope it's something simple like a pot or a dead cap.
 
TLS Guy

TLS Guy

Seriously, I have no life.
I'm still a bit miffed and slightly stubborn xD. I will try and fix it, can't replace it atm so I guess I'll just hope it's something simple like a pot or a dead cap.
In your dreams.
 
George Othen

George Othen

Enthusiast
:p So I took the front panel off, chucked it on the working sub. Seems to be something local to that panel :cool:
 
lovinthehd

lovinthehd

Audioholic Jedi
You might contact Yamaha support....they might be able to assist....
 
TLS Guy

TLS Guy

Seriously, I have no life.
:p So I took the front panel off, chucked it on the working sub. Seems to be something local to that panel :cool:
Here is a service manual. With the problem you describe I would start by running through the test procedures on page 8. You will need a signal generator and a dual channel oscilloscope. You will also need an amplified high impedance meter, called a FET VOM, or an old tube volt meter. Do not plow around with a standard multi meter or you will do a lot of damage.
 
George Othen

George Othen

Enthusiast
I was thinking of just using a standard multi-meter tbh, how come that could cause damage?

I have a rather odd update; it just started working again. I put the front panel back on after checking out the circuit diagram on the back and it appears to work now. Maybe it was just attention deprived xD

As far as an oscilloscope goes, unlikely I can afford a half decent one for a while yet. I could try and use the uni's I guess but as it seems to work now. I'll just hope it continues till I can afford a replacement.

Thinking of acquiring 2 bk ff monoliths.:D

Thank you for all the suggestions!
 
TLS Guy

TLS Guy

Seriously, I have no life.
I was thinking of just using a standard multi-meter tbh, how come that could cause damage?

I have a rather odd update; it just started working again. I put the front panel back on after checking out the circuit diagram on the back and it appears to work now. Maybe it was just attention deprived xD

As far as an oscilloscope goes, unlikely I can afford a half decent one for a while yet. I could try and use the uni's I guess but as it seems to work now. I'll just hope it continues till I can afford a replacement.

Thinking of acquiring 2 bk ff monoliths.:D

Thank you for all the suggestions!
Because standard multi meters have too low an impedance and when testing solid state circuits they draw too much power to drive the meter, and so cause damage.

What is required for service work is amplified meters that have impedance in the megohm ranges, and do not load the circuits.
 
Pedro Alvarado

Pedro Alvarado

Full Audioholic
well, if it's working, leave it alone i guess. maybe it's a crack on one of the solder points?


Sharp LC-60LE632U
HK AVR 3600
Def Tech BP 2004 TL
Def Tech CLR 2002
Def Tech BP2X
AudioSource SW Fifteen
room size 15d 17w 10h
 
Pogre

Pogre

Audioholic Slumlord
I had a similar issue with one of my SB1000's when I owned a pair of them. Turned out to be a bad pot on the amp. Fortunately it was under warranty and they sent me a new amp.
 

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